The present invention relates to internal combustion engines in general and specifically internal combustion engines equipped with water injection. In particular the invention relates to an internal combustion engine having water injected into the intake air stream to improve overall engine efficiency and to reduce NOx, particulate matter and other toxic emissions by cooling combustion gases and by displacing a portion of hydrocarbon fuels.
Water and other aqueous solutions have been injected into hydrocarbon-fueled engines by various ways and means to provide improved operation of said engines, emphasizing a variety of benefits. A water/fuel ratio of as low as one to twenty and as high as one to five is exemplified in related art. In the majority of embodiments water is used to cool and condense the air in the intake air stream. During the compression stroke, water droplets absorb heat produced from prior combustion, preventing pre-detonation and auto-detonation. During the power stroke water subsequently expands to super-heated steam by the burning fuel mixture, increasing the mechanical efficiency of the combustion process. Benefits may also include scavenging and preventing deposits in the combustion chamber of said engines, resulting in improved engine performance and decreased abrasion on internal engine surfaces. Water injected engines are generally reported to run more smoothly with less misfiring. Because adding humidity lowers combustion temperature by enthalpy, water injected engines can be adjusted to run on a leaner air/fuel mixture, thus conserving natural resources. Most significantly, reduction in peak combustion temperature minimizes the formation of oxides of nitrogen and carbon and reduces thermal stress on engine components. U.S. Pat. No. 3,866,579 to Serruys sets forth a method to spray variable amounts of water and increase airflow to the intake of an engine to achieve lower NOx emissions. His method lacks adequate control means and is capable of leaving excessive amounts of water in an intake path after engine shutdown. U.S. Pat. No. 3,915,669 to Minoza suggests a vaporizer carburetor which uses exhaust beat to vaporize water and gasoline and release them into the intake air of a vehicle engine for smooth, responsive acceleration and to reduce the heat of combustion. His device would require new engineering for almost every different engine. U.S. Pat. No. 4,476,817 to Lindberg reports that inducing steam through an ultrasonic device into the air stream of a gasoline-fueled vehicle engine reduced NOx emissions significantly, boosted the engine""s power and smoothness of operation and prevented pre-detonation normally associated with the use of lower octane fuel than factory recommendations. He also reported adjusting the engine to run on a leaner air/fuel ratio. His device would also require special engineering for application on different engines. U.S. Pat. No. 4,960,080 to O""Neill et al. describes a system for the reduction of NOx emissions for a turbo-diesel generator set by means of a steady flow spray nozzle water injector that is switched on at a pre-determined electrical load and switched off as the load demand falls below that sane pre-determined value. His device is very limited in scope and effectiveness under varying conditions. U.S. Pat. No. 5,522,349 to Yoshihara et al. sets forth a water injection system that meters a spray of water into each cylinder of a diesel engine, timed synchronously with fuel injectors to achieve a spray pattern that he purports to be optimal in the abatement of NOx emissions. Their design calls for an entire combustion chamber design change to accommodate both the fuel injection and water injection systems. U.S. Pat. No. 6,170,470 to Clarkson et al. illustrates a water injection system for disposing of water condensate in a gasoline fuel tank by a series of sensors and valves that monitor and maintain an intermittent water injection system. Their system offers no continuity of benefits, but rather is a method for water disposal in rare instances. U.S. Pat. No. 6,414,745 to Hellen et al. describes a pulsating water injection system for a four-stroke diesel engine, synchronous with the intake stroke of each cylinder. They postulate that this is the most efficacious application of water injection for a diesel engine. Their system calls for an entire combustion chamber design change. U.S. Pat. No. 6,289,853 to Walczak et al. sets forth a water injection system for a marine engine, acquiring water for his system from a fresh or salt-water source in which a marine vessel moves. Their primary concern is setting forth a purification process to supply their water injection application. U.S. Pat. No. 4,808,287 to Hark and U.S. Pat. No. 5,464,532 to Nowlin et al. demonstrate effective means of providing a de-mineralized, ultra-pure water supply by passing it through ion exchange media and reverse osmosis systems. Those experienced in the art will recognize the advisability of employing such means. U.S. Pat. No. 6,357,671 to Cewers sets forth a means of ultrasonic vaporization of liquids. Though other references not cited have set forth numerous ways to vaporize liquids ultrasonically, this one is given as an example of a method that could be used to create an aqueous vapor for a water injection system such as the one described in the present embodiment.
As evidenced by these examples, various types of devices have been developed to induce water or other aqueous solutions into the intake air of internal combustion engines. These methods are not only limited in their inability to precisely detect and provide means for optimal engine operation but also are incapable of metering of a continuously optimized volumetric ratio of water in the final fuel/air charge. Spray or steam injection systems also could damage the turbine blades in a turbocharged engine unless injected downstream from the compressor. Injecting hot steam also has a disadvantage in that it doesn""t have as much expansion capability in the power stroke as cool vapor has. In the event that one of the prior art systems did not completely cut of the water supply before engine shutdown, an accumulation of water in the intake manifold or combustion chamber could result in damage to internal engine parts on subsequent start-up or over a protracted period of time. Although this problem is generally recognized as critical to the effective operation of a water injection system none of the prior art adequely demonstrates fail-safe measures to assure a minimal level of humidity in an intake manifold at engine shutdown. Most of the prior art expresses a concern about using unpurified water in a water injection system. However, almost all of them offer no means for the removal of minerals from the water, which produce scale and corrosion. The only one that does incorporate a means of water demineralization is Walczak, et al. and their only reason for doing so is to be able to use seawater in their marine application. Analysis of water in most parts of the world reveals a mineral content that presents a concern for use in an engine. Direct injection of water into the combustion chamber presents similar challenges to other methods, but complicates broad application of its technique by requiring highly specialized controls and injectors, precision machining and an individualized system for every engine style. Related art systems have not been entirely successful in satisfying engine requirements, largely due to their inability to respond adequately to a wide range of engine operating conditions. None of the prior art addresses the monitoring of exhaust gas temperature as a means for continuous precision control of NOx reduction by water injection. Since combustion temperature is the major contributor to the production of oxides of nitrogen, it is essential to introduce an improved method for exhaust temperature measurement and control in order to achieve a more precise NOx control. None of the prior art addresses water vapor injection for emissions control at engine idle speed, which accounts for large volumes of NOx emissions, particularly in urban population areas. None of the prior art addresses water vapor injection for engine coolant temperature control at engine idle speed, which is a major problem in heavy stop and go traffic. It is evident that, for the reasons stated, none of the prior art has provided a water injection system with adequate means to achieve significant technical or commercial acceptance.
It is a general objective of this invention to provide a novel method and system for controlling exhaust gas temperature by controlling the humidity level in the intake air stream of an internal combustion engine, which will reduce harmful emissions, improve performance, increase fuel efficiency and promote longevity of said engine.
More specifically, it is an object of the present invention to provide a novel and unique hydration system and method by which a cool liquid, namely water or other aqueous solution, can be ultrasonically vaporized and introduced at a measured rate into an engine intake air stream, being activated, de-activated and variably controlled, primarily, in conjunction with the exhaust gas temperature of said engine and, secondarily, in conjunction with the power output levels and operating parameters of said engine, ranging from idle speed to fill load conditions. A programmable logic controller or an embedded controller can be programmed to interpret electrical output signals and to automatically control said hydration system to respond with precision to continuously optilize engine performance.
An important object of the present invention is to set forth a novel and unique hydration system that assures the absence of minerals, especially calcium, other dissolved solids and impurities in the water supply, which could be harmful to said hydration system and to said engine. The implementation of current water purification and demineralization technologies can more than adequately perform this task.
A vitally important object of the present invention is to devise a means of assuring the complete evacuation of excess humidity from the intake air stream of an engine before allowing a complete shutdown of said engine. Under normal operating conditions a water injection system such as described in the current preferred embodiment would already be automatically disengaged by the time said engine was shut off by the operator. In circumstances where there was not sufficient time for said water injection system to evacuate excess humidity from said intake air stream before engine shutdown, the installation of an interrupt delay in the ignition system of said engine will provide the extra seconds required to accomplish this objective.
A further object of the present invention is to provide a novel and unique hydration system for the intake air stream of an engine, which is readily adaptable to a variety of engine types and sizes for both stationary and mobile applications.
The present invention achieves these and other objects by providing a system for regulating the emissions discharge of an engine, whether equipped with a turbocharger compressor or by natural aspiration, whether equipped with a fuel injection system or a carbureted fuel-mixing device, being a prime mover for a variety of working applications. Automatic switching activates said hydration system when said engine is under a load and deactivates said system when said engine is in a no-load status. In a matter of seconds after engine start-up exhaust gas temperature can rise to a level that represents a significant production of NOx, hydrocarbons and particulate matter, which need to be controlled. A thermal probe located in the exhaust path of said engine signals an electronic control unit that said engine exhaust has achieved a pre-determined thermal value that corresponds to a specified emissions level. The output of said electronic controller then activates an ultrasonic vaporization unit to achieve an initial level of humidity in the intake air stream. Said ultrasonic unit generates an aqueous vapor ( less than 10 micron droplets) from an ultra-pure de-mineralized water supply. In the present embodiment said aqueous vapor is introduced into the intake air downstream from an air-filtering device and a turbocharger when a pre-designated exhaust gas temperature is achieved, then passes into an intake manifold. In other embodiments said aqueous vapor could be introduced anywhere along an intake air pathway, including being injected directly into the combustion chamber of an engine. As engine exhaust temperature rises, due to increased load or higher ambient temperature, said control unit increases the quantity of said aqueous vapor to counteract increasing emissions and to maintain smooth operation of said engine. The resulting system is both reliable and cost-effective, and is readily adaptable to a variety of engine types and sizes by increasing or decreasing the aqueous vapor necessary to accommodate the range of exhaust temperature differential imposed by the output load of an engine.